If you showed this graph to someone with no labels, the "sharp drops" would be identified at the beginning of 2002, the beginning of 2004, the end of 2005, and the end of 2007. Only one of these has any remote connection to an election, the 2005 one.

The "Bush gas price switch" theory also has to account for the huge price jumps in 2005 and right now, where supposedly the theory would be calling for a badly-needed pre-election dive.

Keep in mind that with a national election of some kind every two years, pretty much ANY graph would have some significant points falling on or near an election.